Saturday, August 13, 2022

Digging is Deadly in this Cook County Forest Preserve.

Within the Palos Park Woods Forest Preserves of Cook County in Lemont, Illinois, about 22 miles southwest of downtown Chicago, in an area named Red Gate Woods, are two spots designated Site A and Plot M. 
This marks the lab's site and proudly states; "World's First Nuclear Reactor," followed by a summarized history of Argonne.
The Manhattan Project's Site A is 19 acres in size and contains the buried remains of the world's first nuclear reactor. 
The World's First Nuclear Reactor, "Site A," was at Red Gate Woods in the Forest Preserves of Cook County.
"Plot M" was a 150 feet by 140 feet area that is a radioactive waste dumpsite.
PLOT M - The word "NO" looks to have been chiseled away. CAUTIONDO  NOT  DIG

Just outside Chicago in the 1940s and 50s, visitors strolling down a wide and worn trail of the Red Gate Woods would suddenly stumble upon a gruff and well-armed garrison of military police. The MPs would pepper the confused strangers with questions, check IDs, and search pockets. Then without an apology or explanation, the confused visitors would be ordered firmly to leave how they came. And NEVER come back.

Chicagoans wouldn't learn for about 20 years later that they had stumbled upon the Manhattan Project's Site A, codenamed "Argonne." The military housed the world's first artificial nuclear reactor, CP-1 (Chicago Pile-1).

Argonne's nuclear reactor was technically CP-2 (Chicago Pile-2). CP-1 had been built and run in an abandoned racquetball court beneath the University of Chicago's original Stagg Field in December of 1942. Envisioned by famous physicist Enrico Fermi, CP-1 hardly seemed like the cutting edge of atomic science. This was a pile of 330 tons of graphite bricks surrounding 5 tons of unrefined uranium metal. It was crude, ugly, and had no shielding to protect the scientists operating it. 

Fermi insisted the primitive clump of bricks would not produce enough energy to harm the scientists. He was right. The world's first controlled nuclear reaction ran less than five minutes at a half-watt power, which was not enough to brighten the world's lowest wattage lightbulb. But it was a start.

Argonne and Site A
As the use of the Chicago Pile improved, concern for the safety of its operators (and the thousands of nearby students) promoted a move a few miles to the west, in the middle of the Forest Preserve District of Cook County, called Site A. The scientists dismantled CP-1, moved it to Site A, and reassembled it into a cube about 25 feet high and 30 feet on each base. This time, Fermi added a few safety elements. Five-foot concrete walls surrounded its sides. Six inches of lead and 50 inches of lumber acted as a lid.

The reactor in Chicago, described by Fermi as "a crude pile of black bricks and wooden timbers," consisted of 360 metric tons of graphite, used as a neutron moderator to slow down neutrons, and was fueled by 5.4 tons of uranium metal and 45 tons of uranium oxide. Because the reactor was designed to operate at very low power, it had no radiation shield or cooling system.

Although assembled from CP-1, this redesigned reactor had earned its name, Chicago Pile-2 (CP-2). A year later, CP-3 joined CP-2, although CP-3 used heavy water (H³O+) instead of graphite to slow nuclear reactions. 

Argonne National Laboratory (Lemont, Illinois) began in the Metallurgical Laboratory of the University of Chicago, formed partly to carry out Enrico Fermi's work on nuclear reactors for the Manhattan Project during World War II.

For a decade, scientists conducted hundreds of experiments using these primitive reactors. The experiments ranged from nuclear weapons to biomedical research to sustained nuclear energy. 

The End of an Era
By 1954, the two reactors had become obsolete artifacts of nuclear energy's early years. It was time to shut down. Engineers cannibalized useable parts or fuel for other reactors. The most radioactive and dangerous elements of the reactors were disposed of by the Oak Ridge Laboratory in Tennessee. The rest would be buried on site. Engineers dug a trench 40 feet long beside the former lab, encased the remains of CP-2 and CP-3 in concrete, and then rolled them into the trench to be entombed forever.

In the early and mid-1980s, amidst the horror of Three Mile Island and Chernobyl, the City of Chicago asked Greenpeace surveyors to test the burial grounds. They were horrified to find islands of radioactive elements dotting Site A, now called "Site A/Plot M Disposal Site." Politely requesting help from the federal government did little good. When the information went public, however, the outcry was epic. People who had spent years strolling those woods, picnicking, and riding horseback now found it had been dangerously radioactive. The federal government gave the city $30 million to fence off, analyze, and decontaminate the site. A decade later, their efforts transformed it into a safe, recreational area, although the site annually goes through a comprehensive survey.

Compiled by Dr. Neil Gale, Ph.D.


  1. My Mom worked on that project, she was considered security back in those days. Her badge number at ANL was 00005

  2. See this WSJ report: for more details.


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